Process of forming water-laid felts containing hollow-viscose, textile, and synthetic fibers



United States Patent 9 Claims. (Cl 162-146) ABSTRAQT OF THE DISCLUSURT.

Process of making a non-woven feltlike fabric on a papermaking machine wherein a specific composition of (A) tubular or partially hollow viscose fibers, (B) normal textile fibers of natural, artificial or synthetic organic polymer fibers and (C) special synthetic polymer fibers having a lower softening range than the other two types of fibers are waterlaid on the papermaking machine, excess water is removed, and the resulting non-woven web is heated to soften and then melt fibers (C) without softening fibers (A) and (C) while maining the web free of any tension or pressure during at least the first stages of the heat treatment. This process permits the non-woven web to contract freely and shape itself into a feltlike product. This product is useful as an artificial felt.

This invention relates to a process for the production of a feltlike fabric, and more particularly, the invention is directed to the production of a non-woven textile sheet material or fabric with a soft felted surface and other feltlike properties analogous to natural felts.

Felts were originally produced from animal fibers, hairs or furs by subjecting the carded slivers or batts to a process of felting and fulling with the application of pressure, heat, moisture and mechanical work. Practically all animal fibers are capable of being felted under such conditions by using carding machines and other apparatus capable of intermingling and working the individual animal fibers into a non-woven matted textile fabric structure. The resulting product can be referred to as a natural or true felt and ordinarily possesses less strength than a woven fabric produced from the same fibers. However, natural felts can be obtained with a wide variance in strength depending upon the fulling agent which is employed and the amount of mechanical work which is applied together with pressure, heat and/or moisture. In addition, binding agents are sometimes employed to provide a substantially stiffer product with higher strength, particularly where the felt is to be used for purposes other than as a textile fabric since binding agents tend to destroy the soft and smooth surface characteristics or handle of the felt.

The property of felting is peculiar to animal fibers, and this characteristic behavior is not generally observed in non-animal fibers, i.e. vegetable or mineral fibers. Likewise, synthetic polymer fibers do not ordinarily have satisfactory felting properties, and it is quite difficult to produce a fabric with a smooth feltlike surface from any of these non-animal fibers. Nevertheless, many attempts have been made to produce feltlike fabrics from nonanimal fibers, either by treating individual fibers so that they will approximate the structural characteristics of animal fibers or else by using various techniques to bond the individual fibers into a non-woven structure.

According to one known process, a synthetic polymer fibrous felt is prepared from polyamide fibers which have first been subjected in the form of a carded sliver or batt 3,394,047 Patented July 23, 1968 to an acid falling, for example, by treatment with formic acid. In another known process, a mixture of polyvinyl acetate fibers and cotton fibers are carded together and the resulting slivcr or batt is heated to a temperature at which the lower melting fiber softens or melts. The molten fiber then acts as a bonding agent to hold the other fibers together, particularly where the fibers cross each other in the sliver or batt. This same procedure is followed in another known process by using a mixture of stretched and unstretched polyethylene terephthalate fibers, each of which have different melting points.

All of these known processes require a fibrous fleece which is initially quite voluminous and is generally prepared by working the fibers together on a carding machine. This voluminous fleece is then strengthened by use of a fulling agent or by using suitable binding agents or bonding fibers dispersed in the fleece and capable of adhering the fibers to each other. The finished product then has about the same voluminous characteristics as the initial fleece, and the dimensions of the fleece remain sub stantially the same throughout the entire process. The carded sliver or batt or fibrous fleece may also be bonded by other methods including the well-known needle process. In general, such methods of producing an artificial felt or bonded fleece require a considerable amount of time and yield a product with properties which are highly dependent upon the success in forming the initial fleece on the carding machine.

In order to obtain a more rapid production of artificial feltlike fabrics, it would be highly desirable to produce the non-woven web or fleece on a papermaking machine wherein the individual fibers can be water-laid from an aqueous dispersion onto the endless screen or similar foraminous supporting structure of the papermaking machine to form the non-woven web. However, previous attempts to use a paperrnaking machine for this purpose have not been satisfactory because the resulting product tends to have a hard, rough or dense surface structure corresponding more closely to paper or parchment than to the desired smooth and soft surface structure of a felt. Such results have probably been considered inherent in the papermaking process itself, in that this process requires the water-laid short staple fibers in the form of a sheet to be conducted through a number of steps for removal of water, drying, and the application of pressure in order to obtain a coherent, continuous sheetlike or paperlike structure. Thus, excess water is first drained from the water-laid fibers on the endless screen or sieve band of the papermaking machine, and additional water is usually removed by pressing the fleece on a second endless felt hand between one or more rollers, usually referred to as the wet press. Finally, the water-laid web is conventionally dried on heated drying cylinders, the web being pressed against the cylinders by co-running felt bands. These various operations favor the development of a paperlike rather than a soft, feltlike product.

Further difliculty is experienced when waterlaying all synthetic fibers and many vegetable fibers on the papermaking machine, because these fibers have a very smooth surface and low swelling properties. As a result, the waterlaid web or fleece does not have sufficient strength to hold together in the papermaking process. Thus, fibers which would be particularly useful in producing a felt do not ordinarily have the necessary strength or other properties which are exhibited by the cellulose fibers normally employed in making paper. In order to avoid this problem, a number of techniques have been employed in order to make it possible to process synthetic polymer fibers and similar smooth natural fibers on the papermaking machine.

For example, various adhesives or bonding agents such as carboxymethyl cellulose have been added to the fibrous dispersion prior to waterlaying on the papermaking machine. These water-laid fleece or web are then consolidated and formed into a stronger coherent web during drying when the fibers tend to firmly adhere to each other. However, since this drying takes place while applying pressure to the adhesive-containing web, the resulting product merely has a flat, paperlike structure. In the absence of any substantial pressure, the fibers usually do not adhere to each other sufficiently to provide a web with satisfactory strength, and there is still no real approximation of a true felt.

In addition, processes have been suggested in which synthetic polymer fibers are mixed with other specially treated polymer fibers referred to as fibrids, e.g. as disclosed in US. Patent No. 2,999,788, and are processed together on the papermaking machine. These fibrids have a particular physical structure which gives them the capacity to hook or link together, thereby imparting a higher strength to the water-laid web, and the resulting web can be further strengthened by melting the polymer fibrids. For the reasons described above, the products of this process likewise are flat and paperlike. If the weight per square meter of the fleece or web is increased in order to achieve products of greater thickness, a solid cardboardlike structure is obtained rather than a fabric with a felt or textile handle.

The principal object of the present invention is to provide a process for the production of a feltlike fabric on a papermaking machine by using a specific mixture of three different types of fibers capable of being waterlaid from an aqueous dispersion and further processed to yield a non-woven fabric product having a much closer approximation to true or natural felts than has been previously possible.

Another object of the invention is to utilize the rapid operation of a papermaking machine for the purpose of producing an artificial feltlike fabric.

Still another object of the invention is to provide a variety of feltlike products by a process which permits a relatively wide variance in the dimensions and density or voluminosity of the resulting felt without losing desirable feltlike properties.

Yet another object of the invention is to provide a novel feltlike product as obtained by the process of the invention.

These and other objects and advantages of the invention will become more apparent upon consideration of the following detailed description of the invention. This description is intended to illustrate the process and roduct of the invention by means of specific materials, and it should be understood that the invention is not limited to such specific materials where equivalent materials may also be used within the scope of the appended claims.

It has now been found in accordance with the present invention that it is possible to produce on a papermaking machine a non-woven feltlike fabric having a smooth textile surface structure by carrying out the following steps. First, there is dispersed in water, preferably with the assistance of a surface active wetting or dispersing agent, a fibrous mixture of (A) to 80% of tubular and at least partially hollow viscose fibers, (B) 10 to 80% of solid textile fibers selected from the group consisting of natural and artificially regenerated vegetable fibers, and synthetic polymer fibers, and (C) 10 to 80% of synthetic polymer fibers having a softening range which begins at least about 10 C. below the softening range of all the other fibers in said mixture; and then waterlaying this fibrous mixture from the aqueous dispersion onto the foraminous support of a papermaking machine with removal of water to form a non-woven water-laid web. This water-laid web is then heat treated under temperature conditions and/or in the presence of steam sufiicient to at least partially melt the fibers (C) without softening the remaining fibers (A) and (B).

Such terms as felt, felted and feltlike are employed herein to describe any textile fabric which has properties and characteristics resembling those of a true felt which has been produced from animal fibers such as wool, hair or fur. The papermaking machine employed for the purposes of this invention is quite well known in the art and does not require a detailed description. Such terms as waterlaying and' water-laid are commonly employed to describe the manner in which a fibrous slurry is caused to flow upon the screen, sieve or other foraminous support of the papermaking machine. EX- cess water is removed through the opening in the screen, and the resulting moist web of fibers can be further dried in subsequent stages of the process. Percentages referred to throughout this specification are by weight unless otherwise indicated.

The tubular and at least partially hollow viscose fibers (A) can be produced by any suitable process which produces bubbles, hollows or cellular gas spaces in filaments spun from a viscose solution. Such modified viscose fibers are generally referred to as hollow filaments, for example as discussed in Natural Polymer Man-Made Fibres by C. Z. Carroll-Porczynski, Academic Press Inc., Publishers, New York (1961), pages 5456. Particularly good results are obtained for the purposes of the present invention by using hollow viscose fibers which have been obtained according to British Patent No. 865,339. However, a hollow or cellular viscose filament can also be obtained by adding to the viscose solution a substance such as calcium carbonate which will evolve gases under the conditions of the spinning bath. Regardless of the manner in which the hollow filaments are initially formed, the initially spun viscose filaments contain entrapped or enclosed gas cells or air spaces which can be subsequently collapsed during the further processing of the filament without departing from an essentially tubular structure. In general, the hollow filaments have a relatively low tensile strength and should normally be used with a denier of between about 1.0 and 5.0. The individual filaments or bundle of filaments are of course cut into staple lengths for suitable dispersion and waterlaying on the papermaking machine together with the other fibers.

In contrast to normally spun viscose filaments, i.e. filaments having a continuously solid cross-section, the hollow viscose filaments or fibers (A) are analogous to cellulose in that they have the capacity of naturally adhering or bonding with each other when deposited from an aqueous dispersion into a water-laid web or sheet and then dried. This natural adherence of hollow fibers to each other is one of the primary reasons for including these fibers in the fiber mixture according to the inven tion. During transport and handling of the water-laid fibrous web or fleece through the papermaking machine and especially during removal of the web from the screen and the initial drying of the web, the hollow viscose fibers act as carrier fibers to impart an essential minimum strength to the fibrous web. In other words, the hollow viscose fibers provide a temporary means of holding all of the fibers together in a coherent and dimensionally stable web or sheet until such time as the fibers are more permanently bonded together during the subsequent heat treatment step to form a feltlike product.

It is also advantageous to employ these hollow viscose fibers in the water-laid fibrous mixture because they can be produced with a relatively wide variation in their natural bonding capacity for each other depending upon variations in the spinning process and the manner in which they are given a cellular or hollow structure. In general, the degree to which these hollow fibers will naturally bond or adhere to each other depend upon the wall thickness of the tubular fiber and the ratio of maximum length to maximum width in the cross-section of the fiber. With this availability of different types of hollow viscose fibers, it is thus possible to predetermine and influence the character or properties of the feltlike final product. Since these viscose fibers have naturally high water-absorption properties, their inclusion in the fibrous mixture imparts absorbency and a soft handle to the feltlike end products of the invention.

The second group of fibers (B) are employed in the invention primarily in order to impart feltlike properties to the finished product. Since this particular group of vegetable and synthetic polymer fibers do not have a natural capacity for bonding or adhering to each other, they cannot be used alone on a papermaking machine in order to produce a satisfactory feltlike product. However, when combined with the other fibers in accordance with the invention, these normally non-adhering fibers (B) act to a certain extent as an inert filler and tend to prevent during the formation of the water-laid web or fleece an excessive number of points at which the tubular or hollow viscose fibers (A) come in contact and adhere to each other. Thus, in the absence of the fibers (B) the hollow viscose fibers (A) would become strongly compressed and adhered to each other so as to yield a paperlike structure with practically no textile or feltlike qualities. Examples of type (B) fibers include the following: polyamide fibers such as polycaprolactam or polyhexamethylene adipamide; polyester fibers, especially polyethylene terephthalate; regenerated cellulose fibers as obtained by the normal spinning of viscose or cuprammonium solutions; and natural vegetable fibers such as cotton linters or natural silk. The synthetic and artificial fibers of this class as well as thenatural vegetable fibers have a continuously solid cross-section and relatively smooth, normally non-felting surface characteristics. In general, all of these fibers can be employed with a denier of about 0.8 to 10.0.

It will be obvious that a careful adjustment must be made in the ratio of the hollow, tubular viscose fibers (A) to the type (B) fibers so as to properly influence the feltlike character of the final product. Although the results obtained depend somewhat on the individual fibers employed as each component of the fibrous mixture, it is generally desirable to employ a weight ratio of (A) (B) of about 2:1 to 1:2. Where the fibers (B) can be extruded or spun with an elongated cross-section, for example in the form of ribbons or bands, they exhibit some of the natural bonding or adhering properties of the hollow viscose filaments in forming a temporarily strong or coherent water-laid web. In this case, a somewhat larger proportion of the fibers (B) is therefore possible.

The third group of fibers (C) can be characterized as bonding fibers since they act as a permanent bonding agent during the heat treatment step of the process. The softening range of these synthetic polymer bonding fibers (C) must be lower than that of all of the other fibers in the mixture under the conditions of the heat treatment step. The term softening range is well understood in this art, and this range is generally accepted as extending from the glass transition point or second order transition temerature up to the crystalline melting point or first order transition temperature of the polymer fibers. In the case of polymers, the melting point is that temperature at which the melt no longer exhibits any double refraction, thereby indicating a complete disappearance of the last traces of crystallinity in the polymer structure. Below this melting point, there is a considerable softening or even a partial melting of the polymer as its temperature increases above the second order transition point. Thebeginning of the softening range can also be defined as that temperature at which the filament, conditioned by a sudden drop in the inner viscosity, begins to lose its original crystalline form under the influence of surface tension. For purposes of the present invention, it is not necessary to completely melt the bonding fibers (C) but they should be at least partially melted within the softening range of these fibers. Although the softening range is normally measured with reference to the dry polymer material, a lower softening range can be obtained when some fibers are heated with saturated stearn.

For the process of the present invention, it is therefore possible to employ certain fibers having a normal softening range which lies only slightly below the softening range of all of the other fibers employed in the mixture. Thus, certain synthetic polymer fibers soften at considerably lower temperatures in the presence of saturated steam and under a pressure corresponding to the particular temperature required with the saturated steam. For example, fibers obtained from copolymers of caprolactam and hexamethylene adipamide have this property of exhibiting a much lower softening range when contacted with saturated steam. Accordingly, it is possible to use any type of synthetic polymer fiber which can in any manner be caused to soften or partially melt at temperatures which are at least 10 C. below the softening temperatures of the remaining fibers in the mixture. This minimum temperature difference of 10 C. is chosen for practical reasons of permitting a relatively easy control of temperature conditions during the heat treatment step so as to be certain of preventing any softening or melting of the type (A) and type (B) fibers. A smaller temperature difference would require extremely close control of temperature conditions, while a greater temperature difference facilitates temperature control during the heat treatment step. Especially suitable polymers for the type (C) fibers includes the following: copolyamides, especially those of caprolactam and hexamethylene adipamide; copolyeste-rs of terephthalic acid, sebacic acid and ethylene glycol; polylaurolactam; or polypropylene.

The amount of the low-melting bonding fibers (C) depends partly on the strength which is desired in the completed feltlike product. In general, the ratio of the bonding fibers (C) to the remaining fibers in the three-component mixture, i.e. the ratio (C) :(A-t-B), should be about 1:4 to 2:3. Especially good results are achieved in accordance with the present invention when using mixtures of fibers containing 20 to 40% by weight of fibers (A), 20 to by weight of fibers (B), and 10 to 40% by weight of fibers (C).

In carrying out the process of the invention, the various fibers of the required mixture are first dispersed in water, preferably in the presence of any suitable wetting or dispersing agent, in order to form a fibrous slurry which can be water-laid on a papermaking machine in the usual manner. For convenience, this fibrous slurry can be prepared in the head box of the papermaking machine. For most purposes, the weight ratio of fibers to water in the slurry should be about 1 to 1000. Depending upon this ratio and the speed of the papermaking screen or other foraminous support, water-laid fibrous webs of varying thicknesses can be produced and it is generally desirable to prepare an initial water-laid web having a thickness of about 0.2 to 2.0 mm. After removing excess water and preferably drying the water-laid web or fleece, it is then subjected to a heat treatment under suitable temperature conditions with or without the use of steam so that the type (C) fiber begins to flow or soften while the type (A) and (B) fibers are essentially retained in their nonsoftened fiber-oriented state. If desired, the drying of the fibrous web or fleece from the papermaking machine can beat least partly combined with the heat treatment steps.

During the heat treatment operation, the low-melting bonding fibers (C) are at least partly melted, in the sense that these fibers soften and increasingly lose their fibrous form, i.e. they become continuously shorter and tend to contract or coalesce into globular drops. The softened and at least partially melted polymer of fibers (C) also tend to collect at those points in the fibrous web in which the individual fibers come in contact with each other, thereby welding or bonding the web at these discrete contact points. During the heat treatment, there is a relatively high shrinkage of the surface area of the web or fleece, associated with a correspondingly high increase in the thickness of the web, and one obtains a relatively strong and soft, feltlike product. This decrease in surface area and corresponding increase in thickness appears to be the result of the initial intimate mingling or interweaving of the bonding fibers (C) with the remaining non-melting fibers, the desired felting result also being influenced by the high melt viscosity of the softened and at least partially melted bonding fibers.

In order to obtain a strong feltlike product, it is desir-able to select suitable bonding fibers (C) which have the best adhesive properties with respect to the other fibers in the mixture. These adhesive properties can be readily determined, and it is also known that good adhesion can be obtained when using bonding fibers of a polymer corresponding most closely to one of the other fibers in the mixture. Thus, when using a polyamide fiber (B), it is helpful to use a lower-melting copolyamide fiber as the bonding material (C). Where strength of the feltlike product is not an essential factor, a wider selection of bonding fibers (C) is possible.

The heat treatment of the web or fleece is most conveniently carried out with hot air or superheated steam at a temperature in or above the softening range of the type (C) fibers and below the softening range of all of the other fibers in the mixture. In order to achieve the highest possible surface area shrinkage and corresponding increase in thickness, the web or fleece must be completely free of tension. This can be accomplished, for example, by transporting the fibrous web on an endless moving belt or screen through any suitable oven or other enclosed heating zone.

If the bonding fibers (C) are of the type which soften at a lower temperature in saturated steam than under normal conditions, the heat treatment step can also be carried out with saturated steam so as to produce a softening of the bonding fibers at a somewhat lower temperature than the normal softening range of these fibers. Of course, it is again essential that the treatment be executed at temperatures under which only the bonding fibers (C) will soften and not the remaining fibers.

According to another embodiment of the invention, the heat treatment step can be carried out in two stages by first heating the web or fleece, e.g. with saturated steam, to a temperature within the softening range but below the melting point of the bonding fibers (C), this first step being carried out without placing any tension or strain on the fibrous web. Then, the web is further heated in a second stage to a temperature above the melting point of the bonding fibers (C) while placing the web under tension, for example, by stretching to maintain the dimensions achieved in the first stage, using any suitable stretching frame, clamping means along the edges of the web or any similar device. Depending upon the choice of the preheating temperature in the first stage of this particular process, it is possible to adjust the surface area shrinkage and corresponding thickness of the web within certain limits, and one can thus vary the size, shape, density and other characteristics as desired in the final product.

It will be obvious that the heat treatment of the fibrous web can be carried out with any suitable heating arrangement, for example with hot air or steam in an enclosed heating zone or with infrared radiators or similar indirect heating means. In general, heating by convection or indirect radiation is preferred, particularly so that one can obtain the desired shrinkage of surface area and increase of thickness of the web during at least an initial heating in the absence of tension. The feltlike characteristics of the product are essentially formed during such heating in the absence of any tension or pressure on the fibrous web, even though the product may subsequently be further heated with tension and/ or pressure in order to vary the physical characteristics of the final feltlike product.

The process of the invention is further illustrated by the following examples, and it will be understood that the invention is not restricted to the specific embodiments of certain fibers, heating techniques and the like as specifically disclosed in these examples.

Example 1 An aqueous fiberdispersion is prepared with the following composition:

(A) 40 parts by weight of tubular viscose fibers, 1.5 denier, 6 mm. staple length;

(B) 30 parts by weight of ribbon-shaped polyamide fibers (polycaprolactam), 1.4 denier, melting point=2l5 C., cutting length 6 mm. staple length;

(C) 30 parts by weight of ribbon-shaped copolyamide fibers, 1.4 denier, 6 mm. staple length, softening point:166 C., the copolyamide being produced from 33% by weight of AH salt and 67% by weight of caprolactam; and

100,000 parts by weight of water with the addition of a reaction product of a fatty alcohol with ethylene oxide as a wetting or dispersing agent.

The fiber dispersion or pulp slurry is worked on a paper-making machine into a water-laid fleece or web and dried. The web is then subjected to a 20 sec. treatment with hot air at 220 C. The resulting feltlike product is five times as thick as the original water-laid fleece. The surface area shrinkage as compared to the original fleece amounts to 19%.

Example 2 An aqueous fiber dispersion is prepared with the following composition:

(A) 40 parts by weight of tubular viscose fibers, 1.5 denier, 6 mm. staple length;

(B) 30 parts by weight of ribbon-shaped polyamide fibers (polycaprolactam), 1.4 denier, 6 mm. staple length; melting point 215 C.;

(C) 30 parts by weight of ribbon-shaped copolyamide fibers, 1.4 denier, 6 mm. staple length, softening point=l72 C., the copolyamide being produced from 30% by Weight of AH salt and 70% by weight of caprolactam; and

100,000 parts by weight of water with the addition of a reaction product of a fatty alcohol with ethylene oxide as a dispersing agent.

The fiber dispersion is worked on a papermaking machine into a water-laid fleece and dried. The fleece is then treated for 20 seconds with hot air at 220 C. The surface area shrinkage as compared to the original fleece amounts to 40%.

Example 3 An aqueous fiber dispersion is prepared with the following composition:

(A) 40 parts by weight of tubular viscose fibers, 1.5 denier, 6 mm. staple length;

(B) 30 parts by weight of ribbon-shaped polyamide fibers (polycaprolactam), 1.4 denier, 6 mm. staple length; melting point -=215 C.;

(C) 30 parts by weight of a copolyamide fiber, 1.4 denier, 6 mm. staple length, softening point=175 C., softening point in saturated steam=130 C., the copolyamide being produced from by weight of caprolactam and 20% by weight of AH salt; and

100,000 parts by weight of water with the addition of a reaction product of a fatty alcohol with ethylene oxide as a dispersin agent.

The fibrous dispersion is worked in the usual manner on a papermaking machine into a water-laid fleece. After drying, the fleece is introduced without any tension or compression into a fixing oven. The oven is evacuated for five minutes, then filled with saturated steam at C., and this steam is allowed to act on the fleece for five minutes. This treatment is repeated once again. There is obtained a soft feltlike product which has ten times the thickness of the original fleece." The surface area shrinkage with respect to the original fleece amounts to 72%.

Examples 4 to 14 Various fiber mixtures were processed in the same manner as Example 1. The results of these experiments are shown in Table I.

TABLE I.COMPOSITION OF THE FIBER MIXTURES IN PARTS BY WEIGHT A B C Ribbon- Ribbon- Ribbon- Viscose Copoly- Copoly- Tearing Surface shaped shaped shaped fibers amide amide length area Viscose polynylon poly- (round fibers fibers Copoly- Polylau- (m)-tested shrinkage, tubular caprofibers ethylene and solid of 80% of 67% ester rolactam according to percent fibers lactam (AH-salt) terephcross- AH salt/ AH salt/ fibers* fibers DIN 53112 fibers thalate section) capro- 33% caprofibers 3 lactam 4 lactam 5 Example No.2

"Ilie copolyester fibers are produced by polycondensation of 80 parts by weight of terephthalic acid diglycol ester and 20 parts by Weight of sebacic acid diglycol ester. Melting point: 208 C.

1 Melting point: 215" C. 2 Melting point 256 0. point: 179 0.

Example 15 A fiber mixture as an aqueous pulp slurry is prepared with the following composition:

(A) 20% tubular viscose fibers, 1.5 denier, 6 mm. staple length;

(B) 40% nylon 6.6 fibers (round and solid crosssection), 1.4 denier, 6 mm. staple length; melting point: 256 C.

(C) 40% copolyamide fibers (30% by weight AH- salt and 70% by weight caprolactam), softening point=172 C., 1.4 denier, 6 mm. staple length;

100,000 parts of water with a dispersing agent as in Example 1.

The fiber dispersion is worked on a papermaking machine into a water-laid fleece with a surface weight of 200 g./m. This fleece is then subjected to a hot-air treatment (230 C. for /2 min), by conducting the fleece through a hot air chamber on an endless screen band. Directly after leaving the hot air chamber, the fleece while still hot is compressed between two closely spaced rollers. There is obtained a feltlike product with a thickness of about 1 mm. and a tensile strength of about 80 kg./cm. This product is excellently suited for the production of a synthetic leather.

Example 16 A water-laid fleece is produced according to Example 15 with a weight of 1-00 g./m. The heat treatment takes place by conducting the fleece on an endless screen hand through a chamber into which superheated steam of 230 C. is blown. At that point in the chamber where the fleece has reached the temperature at which it begins to shrink, saturated steam of 100 C. is blown against the hot fleece, in which process the shrinking of the fleece is additionally augmented. Immediately after leaving the steam chamber, the fleece while still hot is compressed between two closely spaced rollers. There is obtained a feltlike product with a tensile strength of about 40 kg./cm.

Example 17 Using the fiber dispersion according to Example 3, there is produced a water-laid fleece with a weight of 3 Melting point 260 C.

4 Softening point: 175 C. 5 Softening point: 166 C. Softening shrinkage, and again subjected to a heat treatment with saturated steam at 135 C. for five minutes. A soft feltlike product is obtained with a tearing length of about 1100 m.

The invention is hereby claimed as follows:

1. A process for the production of a. non-woven feltlike fabric on a papermaking machine which comprises: dispersing in water a fibrous mixture of (A) 10 to of tubular and at least partially hollow viscose fibers, (B) 10 to 80% of solid textile fibers selected from the group consisting of natural and artificially regenerated vegetable fibers, and synthetic polymer fibers, and (C) 10 to 80% of synthetic polymer fibers having a softening range which begins at least about 10 C. below the softening range of all the other fibers in said mixture; waterlaying said fibrous mixture from the aqueous dispersion onto the foraminous support of a papermaking machine with removal of water to form a non-woven water-laid web; and heat treating said water-laid web under conditions suflicient to first soften and then at least partially melt the fibers (C) without softening the remaining fibers (A) and (B) said heat treatment being carried out free of any tension or pressure on the web at least during the initial stages of heating such that the web contracts and forms a feltlike surface.

2. A process as claimed in claim 1 wherein said fibers (C) are selected from the group consisting of copolyamides, copolyesters, polylaurolactam and polypropylene.

3. A process as claimed in claim 1 wherein said fibers (C) consist essentially of the copolyamide of caprolactam and hexamethylene adipamide.

4. A process as claimed in claim 1 wherein said fibers (C) consist essentially of the copolyester of terephthalic acid, sebacic acid and ethylene glycol.

5. A process as claimed in claim 1 wherein said waterlaid web is first heated in the absence of tension to a temperature within the softening range but below the melting point of the fibers (C) and is then further heated under tension to a temperature suflicient to melt the fibers 6. A process as claimed in claim 1 wherein said waterlaid web is heat treated with saturated steam.

1 1 1 2 7. A process as claimed in claim 1 wherein said water- References Cited laid web is consecutively heat treated first with super- UNITED STATES PATENTS heated steam and then with saturated steam.

8. A process as claimed in claim 1 wherein said heat 3,039,914 6/1962 Relman 162146 X treatment is carried out in the absence of tension and 5 3,156,605 11/1964 Anderer st 162 157 the web while still hot is then compressed to reduce its 3282038 11/1966 Howell X thickness. 9. The feltlike product obtained by the process of LEON BASHORE Prlma'y Examme" claim 1. R. BAJEFSKY, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,394,047 July 23, 19%

Erwin Sommer et al It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 24, "while maining" should read while maintaining Signed and sealed this 17th day of March 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Edward M. Fletcher, Jr.

Commissioner of Patents Aptestin g Officer 

